Catalog # 410A is an aqueous solution of aniline blue WS and Acetic acid. Aniline blue WS is a mixture of dyes and is predominately methyl blue but also contains cotton blue and water blue. It is used In Masson’s trichrome stain procedure. The other solutions required are: Bouin’s fixative (catalog # 456A), Weigert’s hematoxylin A (catalog # 6201A), Weigert’s hematoxylin B (6206A), phosphomolybdic/phosphotungstic acid (catalog # 726A) and 1% acetic acid (catalog # 308A). The country of origin is the United States.